Video Transcript
The diagram shows a simple outline of the passage of water across the root. What structure, indicated by the question mark, will the water move into so it can then be transported through the plant?
To answer this question, let’s look at the transport system in a typical vascular plant. Vascular plants contain specialized vascular tissues that are used for transporting substances. The two main vascular tissues are xylem and phloem. Phloem tissues in plants are mostly composed of living cells called sieve tubes and companion cells. Phloem is involved in transporting sugars and amino acids around the plant. This transport occurs in two directions: from the photosynthetic parts of a plant, such as its leaves, to the rest of the plant tissues and from these other plant tissues back to the leaves.
Xylem, on the other hand, is mostly composed of dead cells called tracheids and vessel elements or members. Transporting these vessels occurs in one direction only, from the roots to the upper parts of the plant like the leaves. The role of the xylem tissue is to transport water and minerals from the soil to various parts of the plant.
As the question asks us what structure the water taken up by the roots will move into, we know now that the structure indicated by the question mark in the diagram must be the xylem.
